Following lithium ion batteries using a nonaqueous electrolyte solution, much interest has been drawn to a lithium polymer battery using a polymer electrolyte due to popularization of small size portable electronic instruments. The battery of this type is advantageous over the lithium ion battery in that it enables much lighter and thinner batteries to be manufactured and makes the battery leak-free. However, some disadvantages may be seen compared with the lithium ion battery such as decreased current characteristics under heavy loads due to solid state electrolyte.
One of causes thereof is thought to be the internal resistance within the electrode and/or interfacial resistance between the solid electrolyte and the electrode in the battery.
The polymer electrolyte is comprised of a matrix of ion-conductive polymer retaining a nonaqueous electrolyte solution therein and produced by casting the nonaqueous electrolyte solution containing a precursor monomer of the ion-conductive polymer onto the electrode and polymerizing the monomer in situ.
JP-A-10218913 discloses that the interfacial resistance between the polymer electrolyte and the electrode may be decreased by decreasing the amount of unreacted monomer and oligomers of the matrix polymer in the polymer electrolyte to less than 30 weight %. Since this technology is not concerned about the improvement of the internal resistance of the electrode, there remains to exist a problem how the internal resistance of the electrode may be improved.